Backrest

ABSTRACT

A backrest for a vehicle seat with a backrest frame including an arching element, running in a planar manner on the backrest frame with the upper and lower end sections thereof, in the backrest longitudinal direction, each fixed to the backrest, or to a component arranged on the backrest and an adjuster device with which the arching of the arching element may be adjusted in a middle region between the both end sections thereof. At least one limiting element is provided on the backrest frame with one end connected to the middle region of the arching element in order to limit the extent of the arching of the arching element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Phase Patent Application of InternationalApplication Number PCT/DE02/03328, filed on Sep. 4, 2002, which claimspriority of German Patent Application Number 101 45 207.1, filed on Sep.7, 2001.

FIELD OF THE INVENTION

The invention relates to a backrest for a motor vehicle seat.

BACKGROUND

A backrest comprises a backrest frame; a curvature forming element whichextends flat against the backrest frame and which is fixed by its upperand lower end sections (seen in the longitudinal direction of thebackrest, i.e. in the extending direction of the spinal column of aperson seated on the seat) on the backrest frame or on a structuralelement mounted on the backrest frame; as well as an adjusting devicewith which the curvature of the curvature forming element can beadjusted in a region between the two said end sections (hereinaftercalled the middle region).

With a vehicle seat of this kind there is the problem that as the bowingof the curvature forming element increases, its curvature becomes verymarked in the middle region, which goes against the desired largesurface area contact of the curvature forming element against the seatcushion and the large surface area support of the back of a vehicleoccupant associated therewith.

SUMMARY

The object of the invention is to provide a backrest which ischaracterised by a large adjusting region of the curvature formingelement through a large surface area support of the back of the personseated on the seat.

According to this at least one limiting element is provided on thebackrest frame and is connected by one end to the middle region of thecurvature forming element in order to limit the degree of bowing of thecurvature forming element.

The degree of bowing which is thereby to be permitted in each individualcase (i.e. with a specific backrest) is fixed through the choice of anappropriate limiting element.

In that the (preferably elongated) limiting element is fixed by one endon the seat frame or a structural assembly mounted thereon and by theother end on the middle region of the curvature forming element, themaximum extension of the limiting element across the extension plane ofthe backrest frame limits the maximum bowing or curvature of thecurvature forming element. An increase in the curvature is equal to anincreasing distance of individual points of the curvature formingelement from the backrest frame. By limiting the maximum possibledistance of the middle region of the curvature forming element from thebackrest frame through a limiting element to a maximum value it is alsopossible to fix at the same time the maximum possible curvature.

By the middle region of the curvature forming element is thereby meantthe entire region which extends between the upper and lower end sectionsof the curvature forming element (viewed in the longitudinal directionof the backrest). The middle region comprises therefore expressly notonly a region surrounding the centre point of the curvature formingelement, but rather any region which extends between the upper and lowerend section of the curvature forming element and thus between the upperand lower fixing points of the curvature forming element and is spacedtherefrom. It is however advantageous throughout if the middle regionextends around the centre point of the curvature forming element.

The limiting element is preferably formed by a tightening element, e.g.in the form of a cable, belt or wire which becomes taut as the curvatureof the middle region of the curvature forming element increases andwhich ultimately permits no additional curvature once the tension issufficiently taut.

Furthermore the limiting element can also be formed by an elasticallydeformable traction means, e.g. in the form of an elastically deformableplastic rod.

Depending on which curvature is desired with a specific type of backrestit is also possible to provide several limiting elements of the saidkind which can be arranged side by side both in the longitudinaldirection of the backrest and across the longitudinal direction.

The solution according to the invention can be used independently of thetype of adjusting device used for adjusting the curvature of thecurvature forming element. For example an adjusting device can be usedhere where a tensioning element acts on the curvature forming element orwhere a curved body such as e.g. in the form of an eccentric disc servesas the adjusting element.

If a tensioning element such as a cable or wire is used as the adjustingelement then the limiting element can be fixed by its end remote fromthe curvature forming element on the adjusting element. In this case theadjusting element for adjusting the curvature as well as the limitingelement for restricting the curvature of the curvature forming elementform one structural assembly which can be supplied fully pre-assembledwhere applicable.

The solution according to the invention is furthermore independent ofwhether between the backrest frame and the backrest cushion of a vehicleseat there is only one single curvature forming element on which on oneside an adjusting device acts for adjusting the curvature and which onthe other side bears against the backrest cushion, or whether betweenthe backrest frame and the backrest cushion there are two or more largearea elements which interact to adjust the curvature of the backrest.The limiting element provided according to the invention can be usedwith any type of curvature forming element which serves to fix thecurvature of the backrest of a vehicle seat.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention will now be explainedin detail with reference to the following description of an embodimentillustrated in the drawings.

They show:

FIG. 1 a a plan view of an curvature forming element for the backrest ofa motor vehicle seat;

FIG. 1 b a section through the curvature forming element according toFIG. 1 a in a non-curved state;

FIG. 2 a section through the curvature forming element according to FIG.1 a in a markedly curved state;

DETAILED DESCRIPTION

FIGS. 1 a and 1 b show a large surface curvature forming element 1 whichis mounted against a backrest frame 6 of a vehicle seat serving as thelordosis support for a vehicle occupant and shown only diagrammaticallyin FIG. 1 a.

The base body of the curvature forming element 1 is substantiallyH-shaped and has two side sections 11, 12 which extend in thelongitudinal direction L of the backrest and are connected together by across bar 13. The side sections 11, 12 of the curvature forming element1 each have bent over side ends 11 a, 12 a and a reinforcement rib 14and are hereby formed stiffer than the lighter bowing cross bar 13. Theside sections 11, 12 of the curvature forming element 1 are thereby eachpartially uncoupled from the cross bar 13 through a slot 15 extending inthe longitudinal direction L of the backrest.

The backrest longitudinal direction corresponds when the backrest isupright (according to the illustration in FIG. 1 b) to the vertical axisof the vehicle (z-axis) which extends from the vehicle floor to thevehicle roof.

In order to adjust the bowing of the curvature forming element 1 andthus a backrest cushion P mounted in front of the curvature formingelement 1, shown diagrammatically in FIG. 1 b, a tensioning element 2 isprovided in the form of a traction member of wire which is mounted onthe backrest, more particularly on the backrest frame. The tensioningelement 2 is fixed in the region of its lower end 22 through atransverse connecting element 25 and fixing elements 27 connectedthereto to corresponding fixing points 17 a on the lower end section 17of the curvature forming element 1. (The fixing of the tensioningelement 2 in the region of its lower end 22 to the transverse connectingelement 25 is shown diagrammatically in FIGS. 1 a and 2 by a blackfixing spot).

The curvature forming element 1 is on the other hand fixed in the regionof its upper end section 16 in the region of upper fixing points 16 a tothe backrest frame (not shown in the figures) of the vehicle seat bysuitable fixing elements 26 which are connected together through atransverse connecting element 25′. As opposed to the lower transverseconnecting element 25 however the upper transverse connecting element isnot connected to the tensioning element 2.

In short the upper end section 16 of the curvature forming element 1 isfixed directly on the backrest frame through fixing points 16 a andthrough fixing elements 26 (connected together by means of the uppertransverse connecting element 25′) whilst the lower end section 17 ofthe curvature forming element 1 is fixed on the tensioning element 22through fixing points 17 a, fixing elements 27 and a lower transverseconnecting element 25.

In order to adjust the bowing of the curvature forming element 1 a forceis exerted on the tensioning element 2 by means of a manual or electricdrive unit so that the lower end 22 is moved upwards along the verticalvehicle axis (z-axis) in the longitudinal direction L of the backrest.At the same time the lower end section 17 of the curvature formingelement 1 is hereby raised since this is fixed on the lower end 22 ofthe tensioning element 2 through fixing elements 27 and the transverseconnecting element 25.

The upper end section 16 of the curvature forming element 1 remainshowever spatially unchanged since it is fixed directly on the backrestframe through the associated connecting elements 26.

As a result by exerting a force on the tensioning element 2 upwards inthe direction of the vertical vehicle axis z the lower end section 17 ofthe curvature forming element 1 is moved up towards its upper endsection 16. The two end sections 16, 17 hereby move closer together andthe curvature forming element 1 is curved or bowed to an increasingamount, see the change in the curvature forming element 1 from thenon-curved state (FIG. 1 b) into the curved state (FIG. 2).

Basically the increase in the bowing also leads to an increase in thecurvature of the curvature forming element 1 which with a very markedcurvature goes against the desired largest possible surface support ofthe back of a vehicle occupant over the curvature forming element.

Here however the bowing and thus in particular the curvature of thecurvature forming element 1 in its middle region between the two endsections 16, 17 is restricted by two limiting elements 3, 4 (hold-downplates) which are each fixed by one end 31, 41 on the tensioning element2 and by the other end 32, 42 on the cross bar 13 of the curvatureforming element 1. The two longitudinally extended limiting elements 3,4 are thereby mounted on the upper and lower ends of the cross bar 13spaced from each other in the longitudinal direction L of the backrest.

In the non-curved state of the curvature forming element 1 illustratedin FIG. 1 b the limiting elements 3, 4 which are made of plastic areeach deformed so that despite their elongated design they are locatedbetween the tensioning element 2 and the cross bar 13.

As the bowing of the curvature forming element 1 increases, so thelimiting elements 3, 4 become aligned in a straight line, see FIG. 2.The length of the limiting elements 3, 4 with a rectilinear alignmentdefines the maximum distance from the tensioning element 2 (and thus thebackrest frame overall) which the cross bar 13 can occupy across thelongitudinal direction L of the backrest. The bowing of the curvatureforming element 1 is hereby restricted which increases with increasingdistance of the middle region of the curvature forming element 1 fromthe tensioning element 2. It can clearly be seen that the curvatureforming element 1 bears with a large surface area against the backrestcushion P even in the state of maximum curvature illustrated in FIG. 2,and thus enables the back of the occupant to be supported with the largesurface area.

The curvature forming element 1 need therefore not adjoin the backrestcushion P directly. It is possible throughout to provide an additionalbackrest shell between the curvature forming element 1 and the backrestcushion P.

Furthermore the invention can be designed with any type of means foradjusting the curvature of the curvature forming element 1. The use oftensioning means 2 described here for adjusting the curvature of thecurvature forming element 1 is therefore only given by way of example.When using other means for adjusting the curvature of the curvatureforming element 1 the ends 31, 41 of the elongated limiting elements 3,4 remote from the curvature forming element 1 are advantageouslyattached to the seat frame (backrest frame).

1. A backrest for a vehicle seat comprising: a backrest frame; acurvature forming element which extends with a flat area adjacent thebackrest frame and which is fixed on the backrest frame or on astructural element mounted on the backrest frame by at least one of anupper end section and a lower end section in the longitudinal directionof the backrest; and an adjusting device with which a bowing of thecurvature forming element is adjusted in a middle region between theupper and lower end sections; wherein on the backrest frame or on astructural element mounted on the backrest frame there is at least onelimiting element which is connected by one end to the middle region ofthe curvature forming element in order to limit the extent of curvatureof the curvature forming element.
 2. The backrest according to claim 1,wherein the limiting element is elongated.
 3. The backrest according toclaim 1 or 2, wherein the limiting element is tautened as the bowing ofthe middle region increases.
 4. The backrest according to claim 1,wherein the limiting element is elastically deformable.
 5. The backrestaccording to claim 1, wherein the limiting element is formed by tractionmeans which as the bowing of the curvature forming element increasesexerts a tensile force on its middle region.
 6. The backrest accordingto claim 1, wherein the limiting element is formed by one of anelastically deformable plastic element, cable, belt and wire.
 7. Thebackrest according to claim 1, wherein the limiting element is fixedwith the other end on the backrest frame or on a structural elementmounted on the backrest frame.
 8. The backrest according to claim 1,wherein several limiting elements are provided.
 9. The backrestaccording to claim 8 wherein the limiting elements are mounted onebehind the other in the longitudinal direction of the backrest.
 10. Thebackrest according to claim 1 wherein the adjusting device has as anadjusting element which acts on the curvature forming element (1) one ofa tensioning element and a curved body.
 11. The backrest according toclaim 1 wherein the limiting element is fixed with its other end on anadjusting element of the adjusting device which acts on the curvatureforming element.
 12. The backrest according to claim 1 wherein betweenthe curvature forming element and a backrest cushion mounted in front ofthe curvature forming element there is a support element which extendsover a large surface area.